The present invention relates to a device for the metered delivery of a liquid washing or rinsing agent, for a washing machine, such as a laundry-washing machine or a dish-washing machine.
More specifically, the invention relates to a delivery device comprising                a casing which is to be secured to the machine and in which are provided        a refillable receptacle for the liquid agent, which receptacle is capable of containing an amount of the agent corresponding to a plurality of metered amounts, and        an electrically controlled delivery valve device associated with an opening in the receptacle and capable of permitting a flow of liquid agent from the delivery receptacle towards the washing chamber of the machine.        
Devices for the delivery of rinsing agents for dish-washing machines are known in which a level-indicator device is provided in a refillable reservoir and is capable, when the door of the dish-washing machine is open, of providing a signal indicating the level reached by the rinsing agent in the reservoir, that signal being usable to generate an indication of the need to refill the reservoir. In the course of an operating cycle of the machine, an amount of liquid rinsing agent is delivered by activating an electromagnetic delivery valve device associated with a delivery receptacle which, when the door is closed, is in the uppermost portion of the above-mentioned reservoir. The repeated excitation of the delivery valve device enables the total amount of rinsing agent delivered to be varied, for example, as a function of the detected hardness of the water fed into the machine for the rinsing operation. The repeated activation of the valve device involves the generation of an irritating noise, in particular if this device operates with alternating current. With direct current electromagnetic valve devices it is possible to mitigate this disadvantage but the use of direct current devices involves recourse to rectifier circuits, which is unfavourable from the point of view of costs.